Broken HTTP2 cancellations tests

[karpetrosyan]

Sometimes http2 connection cancellation tests fail, but other times they succeed.

The issue appears to be in AsyncHTTP2Connection'sasync_handle_request method, which cannot always handle cancelled errors.

If the cancellation happens in this section of the code, the connection will not call the response_closed method.

[lovelydinosaur]

(As a starting point...)

Sometimes http2 connection cancellation tests fail, but other times they succeed.

Could you provide a link/example for this?

[zanieb]

https://github.com/encode/httpcore/actions/runs/5532888849/jobs/10095604921#step:7:66

[karpetrosyan]

You can get that error by inserting anyio.sleep in the middle of this code block.

Like so

self._sent_connection_init=True# Initially start with just 1 until the remote server provides# its max_concurrent_streams valueself._max_streams=1local_settings_max_streams= (
self._h2_state.local_settings.max_concurrent_streams
)
self._max_streams_semaphore=AsyncSemaphore(local_settings_max_streams)
awaitanyio.sleep(0.5)
for_inrange(local_settings_max_streams-self._max_streams):
awaitself._max_streams_semaphore.acquire()
awaitself._max_streams_semaphore.acquire()

This line may cause a Canceled Error, which we do not handle. We use timeout 0.01 in tests, so I frequently get failing tests on my local machine.

awaitself._max_streams_semaphore.acquire()

[karpetrosyan]

Issue: #756